Flexible kite



March 6, 1956 W. M. ALLISON FLEXIBLE KITE Filed Sept. 8, 1950 Inventor G tT rneg United States Patent FLEXIBLE William M Allison, Payton, Ohio Application September 8', 1950, Serial No. 183,870

4 Claims, (Cl. 24.4 -1 53);

This invention relatesto kites. It proposes a novel'nse of aerodynamic principlesto obtain flight characteristics and ease of operation heretofore unknown in kites.

A; more specificobject of the invention is to present a kite possessinginherent means of compensating for'variations in air stream velocity and air turbulence whereby the kite may maintain a normal attitude offlight and con tinue to be air borne irrespective of such conditions.

Another object of the invention is to present a kite offering a minimum resistance to air flow whereby it is unlikely to be damaged and is easy to -control..

A further object of' the invention is to present a kite which can be economically'andieasily'made,

Still another object of the invention is'to present-a kite which can be compactly'folded when not inuse and which is at all times ready to be releasedfor flight.

A further object of: the invention is to provide a kite of the character described having the advantageous structural' features and the inherent meritorious characteristics and mode of operation hereinafter set forth.

The inventive concept makingxpossible achievement of the above objects is that ofpolymorphic'kite, that is one capable of assuming many shapes, all as may be dictated or required by fluctuations of the air stream. According to this conception of the invention, a kite comprisesa flexibl'e air foillpanel capable of lateral arching for inflation by the air streambnt'braced against longitudinalflexing, and tethers connected to side edges of the panel an 39 .36g together to form a bridle attachable to a flight line. The tethers provide a transverse axis of. restraint about which the air foil panel may bodily oscillate to vary the angle of incidence of the panel relative to such line of restraint andthe angle of attack thereof; relatively to the air'stream, which axis is lengthened or shortened in responsetmvariations in the degree of inflationaofithe panel. According to the construction and mode of operation of the kite c om pensatory adjustments in the angle ofinq denceofthe air foil panel and in the degree of inflation of the panel and in the shape of the inflated arch make possible the maintenance of a favorable attitude of flight under substantially any conditions; ofi air velocity turbulence.

With the above primary and other incidental objects in view as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the features of construction, the parts and' combinations thereof, and the mode of operation, as hereinafter described or illustrated in the accompanying drawings, or their equivalents.

In the drawing, wherein is illustrated the preferred but obviously not necessarily the only form of embodiment of the invention:

Fig. 1 is a view of a kite in accordance with the instant invention, tethered to a flight line and in an attitude of flight like that assumed during ascent;

Fig. 2 is a view in front elevation of the air foil panel;

Fig. 3 is a view of the kite in flight attitude as it appears under conditions of high air stream velocity and with the 2,737,360 Eatented Mar. 6, 1956 "ice 2 center or inflationaryand flight sustaining lines of efiort in line with the longitudinal. axis of the kite, the air foil panel being at a minimum angle of attack and maximum inflation, with the inflation being equal over the surface ofthe panel; i

Fig. 4- is a view simil'ar'toF-ig. 3with the center of effort shifted to the right, as may result from air turbulence; and

Fig. 5' is a view similar to Fig. 3-showing the kite at the opposite end of its operational range, the air foil panel thus being at maximumtattack and'mihimum inflation.

Like parts are indicatedby similar characters of ref; erence throughout the-several views;

Referring to the drawing, and. particularly to Figs. 1 and'2, a kite in accordance with the instant invention may comprisean air foil panel 10*made of any light material relatively impervious to the-passage of air, for example, paper; The shape of the air foilpanel is approximately an isosceles trapezoid, there being present the essential elements of an isosceles trapezoid including a base 11', an apex 12" and interconnecting sides- 13of equal length. The base angles are cropped, as well as the apex 12, to define an irregular hexagonal figureand' lateral extremities 14 longitudinally spaced from the base 11. The marginal area of the air foil panel 10'is folded back upon and ad hesively bonded-to thesurface of the panel to define a reinforced perimeter 15 whereby the panel presents a relatively strong, thin edge to flowing air currents. Extending longitudinally'of the air foil panel 10', from base 11 to apex 12, is a plurality of substantially rigid members 16 Made ofjthin, lightweight, strips of wood or metal tubing and adhesivelybonded" or otherwise secured? to the panel; 10, themembers 16; are arranged centrally of the panel and in interconnecting relation to the ends of the base andiapex thereof I Connected to the lateral extremities 14, as by insertion into the reinforcedperimeter 1 5, are elongated tethers 17 of equal predetermined length. At their 'free ends the tethers 17 are joined'togetherto form a bridle attachable, as shownin Fig. 1', to a flight line 18. Such bridle is of a yielding nature sothat the ends or extremities 14 may move i'n approaching and withdrawingdirections relatively to one another,

In consideringtlie structure of the kite, it will be noted thatwhile-the memberslffifunction aslongitudinal braces, substantially. to preclude flexing or arching of the panel about a transverse axis, there is an absence off lateral rigidity. When not in: use, therefore, the kitemay be folded lengthwise and in usemay flex or arch in inflationary manner about a longitudinal line.

Theeflect' of attachment ofthe tethers 17- to the lateral extremities 14 is to enable the kite to be maintained in an attitude of flight and also to establish stress points defining; a lateralline ofi restraint from which tension forces; can radiate across the airfoilpanel when inflated. Further such line of'rest-rai'nt serves as a pivot for longitudinal bodily shifting of the kite, the surface of the panel 10 assuming variousangles of incidence with respect to-su ch lateral line of restraint as effected and controlled by: theain stream.

Inoperation, the kite is launched simply by releasing it into the wind. The passage of air through the loose folds of the air foil panel 10 causes distension or inflation of the panel into a lateral arch. At the same time, the kite assumes a high deflective angle with respect to the air stream, as for example as seen in Fig. 1, wherein the apex end 12 points downwind and toward the ground. The thrust of the air will rather quickly rock the kite to a more generally horizontal position which it maintains in flight. Facing endwise into the wind, with base 11 as the leading edge and apex 12 as the trailing edge, the kite is borne by the flow of air across its curved under surface. In such position, it offers but slight resistance to the air flow, there being only the thin edge of panel 10, the diameter of tethers 17 and the small ends of brace members 16 to oppose passage of the air. In response to diminishing and increasing air currents there is a corresponding adjustment both in the angle of attack of the panel to the air stream and in the curvature of the panel. Thus, a diminishing air current velocity will allow the trailing end 12 of the panel to drop downward and at the same time will reduce the tension tending to spread apart the lateral extremities 14. These extremities will accordingly approach more closely together and increase the curvature of the air foil panel. The position of the kite in a minimum aspect of inflation and maximum angle of attack is shown in Fig. 5. In Fig. 3 is shown the opposite extreme of the operational range, achieved in response to increasing air current velocity. In this position of the kite, the angle of attack to the air stream is at a minimum while inflation of the kite is at a maximum. An infinite number of automatic adjustments between these operational extremes may be made in compensation for increase and decrease in air stream velocity to maintain in the kite continuous stability in flight.

In a turbulent air stream, the action of fluctuating, nonuniform pressures on the surface of the air foil tend to force the kite out of its normal flight attitude. If generally vertical in nature, these pressures will merely cause the kite to gain or lose altitude. If horizontal, however, a compensating action of the panel is required if the kite is to maintain its fli ht attitude and not progress into a dive. Such action is enabled by the lateral flexibility of the panel which permits it to change shape eccentrically and so cause the center of inflationary efforts to shift. Comparing Figs. 3 and 4, for example, in Fig. 4 the center of inflationary effort has shifted rightward from the longitudinal axis of the kite resulting in a relatively greater inflation of the right hand side of the panel than the left. Excess air currents applied to the right of the panel accordingly may spill over the edge thereof. At the same time the left side of the panel presents a broadly curved surface utilizing all available air to maintain a state of balance with the right side. In the operation of the kite, therefore. the inflationary and flight sustaining lines of effort radiate from a center which is a variable having no physical connection with the kite but restricted to a range of movement within the lateral dimension of the panel 10.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise but one of several modes of putting the invention into effect.

Having thus described my invention, I claim:

1. A kite, including a flexible air foil panel presenting a relatively broad base defining the leading edge thereof and an opposite smaller end defining the trailing edge, tethers connected to the side edges of said panel adjacent said leading edge and joined together at their opposite ends to form a bridle, and means for bracing said panel against longitudinal flexure, said panel being capable of rocking bodily against the restraint of said tethers and of inflating laterally whereby changes in the velocity of the air streams may be compensated for by automatic adjustments in the angle of attack of the panel to the air stream and in the degree of inflation thereof.

2. A kite, including a flexible air foil panel flat in cross section and preventing leading and trailing edges, longitudinal stiffening means precluding material flexing of the panel in a fore and aft direction, there being an absence of lateral rigidity enabling inflation of the panel by the air stream, and a bridle connected to the opposite sides of said panel at aligned points intermediate said leading and trailing edges, said panel responding to changing air stream velocity by a bodily adjustment about said points and by an increase or decrease in inflation.

3. A kite, including a flexible air foil panel flat in cross section and presenting leading and trailing edges, longitudinal stiffening means precluding material flexing of the panel in a fore and aft direction, there being an absence of lateral rigidity enabling inflation of the panel by the air stream, and a yielding connection between aligned points at the sides of said panel to establish a transverse line of restraint variable in length with variations in the degree of inflation of the panel and about which the panel is bodily adjustable to vary the angleof attack to the air stream, said panel having an operational range represented at one extreme by a maximum angle of attack and a minimum inflation and at the other extreme by a minimum angle of attack and maximum inflation.

4. A kite comprising an airfoil member of flexible material capable of being arched by a supporting airstream and being shaped so as to effect a conical arch of the surface thereof transversely across the airfoil memher, the crest of said arch being the longitudinal axis of said airfoil member, and bridle strings attached to said airfoil member on opposite sides of the longitudinal axis serving to guide and control said kite and present the surface thereof at a suitable angle of attack.

References Cited in the file of this patent UNITED STATES PATENTS 1,617,976 Wickersham Feb. 15, 1927 2,107,808 Van Ittersum Feb. 8, 1938 2,386,762 Wheelwright Oct. 16, 1945 2,463,135 Bach Mar. 1, 1949 2,546,078 Rogallo Mar. 20, 1951 FOREIGN PATENTS 261,877 Great Britain Dec. 2, 1926 OTHER REFERENCES Baughmans Aviation Dictionary, 1942 (2nd edition, 1st printing), Aero Publishers, Inc., N. Central Ave., Glendale, Calif, page 31. 

